1. Technical Field
The present invention relates generally to an improved data processing system and in particular to an optical disc streaming architecture. Still more particularly, the present invention relates to a method and apparatus for transferring data from an optical disc.
2. Description of the Related Art
Multimedia involves the combination of sound, graphics, animation, and video. A multimedia data processing system is designed to present various multimedia materials in various combinations of text, graphics, video, image, animation, sound, etc. Such a system is a combination of hardware and software. The hardware runs under the control of an operating system and multimedia application programs.
Multimedia applications impose heavy demands on the operating system to move large amounts of data from device to device, from system memory to a device, or vice-versa, in a continuous, real-time manner. Multimedia systems must support a flexible yet consistent means for transporting these large amounts of data, and control this activity accurately in real time. Data is often stored in some form of mass memory, such as a magnetic disc or optical disc. In particular, compact disc read only memory (CD-ROM) is a form of storage characterized by high capacity (roughly 650 megabytes). CD-ROM drives use laser optics rather than magnetic means for reading data. Another form of optical mass storage is a digital video disc (DVD).
Currently, optical storage devices are being improved to increase the speed of data transferred from an optical storage device for use in a data processing system. With respect to CD-ROM drives, an embedded processor is used to monitor and control the transfer of data from a CD-ROM drive to the bus in a data processing system. Presently available embedded processors used in CD-ROM decoder circuits are not fast enough to handle the bit rates provided by newer CD-ROM drives while also handling other control and housekeeping functions for the CD-ROM drive.
Therefore, it would be advantageous to have an improved method and apparatus for handling data flow from a CD-ROM drive.
The present invention provides an improved method and apparatus for transferring data in a CD-ROM system. The CD-ROM system includes a buffer manager means for identifying the capacity of a buffer memory used to store data from a disc. The buffer manager controls the transfer of data into and out of the buffer memory. Each time a sector of data is transferred from a disc into the buffer memory, a counter is incremented to track the amount of data in the buffer memory. If the counter equals the capacity of the buffer memory, the transfer of data from the disc is halted. Further transfer of data is not allowed until buffer memory is available.
Additionally, the present invention provides an error correction unit that is placed in line with data being read from the disc into the buffer memory.
Each time a sector of data is transferred from the buffer memory to the host, the same counter is decremented. If the counter equals zero, host transfers are automatically halted (without intervention from the processor) and are restarted (again, without processor intervention) when new data becomes available.